Currency detection and verification has been performed in complex currency processing devices such as those described in U.S. Pat. No. 5,960,103 to Graves et al. for “Method and Apparatus for Authenticating and Discriminating Currency”; U.S. Pat. No. 6,883,706 to Mastie et al. for “Point-of-Sale Bill Authentication”; and U.S. Published Application No. 2007/0108265 A1 disclosing “Currency Note Identification and Validation.”
None of these is suitable for a portable, hand-held currency detection and verification device, such as would be useful for a visually-impaired user to verify currency to be paid or received.